I. Field of the Invention:
This invention relates generally to materials handling apparatus, and more specifically to an improved means for stacking products one atop the other as they are transported from a supply station to a wrapping station.
II. Discussion of the Prior Art:
In packaging products for distribution, it is sometimes desired that the products be arranged in layers or stacks prior to being wrapped in plastic film, foil or paper. For example, bakery items such as cookies, buns, confectionary items, etc., are often stacked two, three or more high in a tray or box prior to being enveloped in a suitable film wrapper. Similarly, frozen meat or fish patties are often stacked prior to being wrapped. It is, of course, desirable that the stacking operation be automated and that the stacks be created and transported to the wrapping station at a speed compatible with the overall speed of the supply source and the high-speed wrapper. To avoid the need for machine shut-down or intermittent operation, it is imperative that the stacking system not only work continuously at high speeds, but in a reliable fashion and without damage to the products being stacked.
In the Joa U.S. Pat. No. 2,324,930, there is depicted an arrangement for receiving products in serial order and creating a stack of a predetermined height which involves a vertically oriented conveyor, having a plurality of outwardly projecting arms secured thereto, positioned downstream from and adjacent to a horizontally extending product supply conveyor. The vertically-oriented conveyor is synchronized with the supply conveyor such that, as an arm on the vertical conveyor passes by the end of the supply conveyor, a product is discharged from the supply conveyor onto the arm and carried upward prior to turning 180.degree. and descending. Also included is a synchronized discharge conveyor having a plurality of pushers affixed thereto, the pushers being of a predetermined height so as to simultaneously engage a plurality of products on adjacent arms of the vertical stacking conveyor. As the discharge conveyor moves, the pusher fingers engage a stack of products on the arms and urges them free of these arms.
Another machine for accomplishing a similar end. i.e., stacking products, is disclosed in the Rose U.S. Pat. No. 4,413,462. In the case of this machine, sandwiched cookies are delivered from a conventional sandwiching machine and stacked into two-high stacks before being transported to a wrapping machine. In this machine, first and second rows of cookies leaving the sandwiching machine are transported along parallel conveyor branches, with one such branch being elevated relative to the other and offset therefrom in a side-by-side relationship. The upper branch has a diverter which extends obliquely to a point where its end overlies the lower conveyor. As the respective products move along their respective conveyor branches, a point is reached where the two conveyors merge in a common vertical plane allowing cookies discharged from the uppermost conveyor to come to rest on top of other cookies progressing along the lower conveyor.
While the machines described in the aforereferenced Joa and Rose patents function to stack product prior to wrapping, in each instance, the machines in question are unduly complicated and would appear to be subject to severe problems in terms of maintaining synchronization over prolonged periods of operation. It is the purpose of the present invention to obviate such problems.